Sarah Hyland at the CMT Music Awards in Nashville, Tennessee. Photo / AP

Modern Family star has revealed she spend her weekend in hospital with a mysterious illness - and she's still unsure what was wrong.

Speaking to fans on her Instagram story, Sarah Hyland says she went into hospital after feeling like she "couldn't breathe".

"Long story short, I went in because I was feeling like I was being choked from whatever's in the house," she said.

"They ran multiple tests, multiple times, and there's nothing physically wrong with me," she said. "So wonder why I was there."

The 28-year-old star went to the emergency room on Friday night and was released on Monday morning, according to the New York Post.

Hyland has been candid about her health battles before, having suffered from kidney dysplasia since she was a baby.

In 2013, her father Edward Hyland donated his kidney to help alleviate her symptoms. However in December last year, she had her second transplant from her brother after her father's donated kidney started to fail.